1. Field of the Invention
This invention relates to sheet metal nails and more particularly relates to improvements in sheet metal roofing nails for use in roofing structures and the like in which the nail is driven into a thickness of sheet steel or other sheet metal to secure a pad or layer of insulation or similar material thereto.
2. Description of the Prior Art
Sheet metal nails such as sheet metal roofing nails are well known in the prior art. Such nails are generally T or L shaped in cross-section comprising a generally flat head portion and a shank portion extending generally perpendicular from the head portion. The shank portions have a V shaped leading edge designed for piercing at the end most distant the head portion. The shank portions are generally provided with at least one locking member, or tang, for lockingly engaging the underside of the media into which the nail is driven. Many nails utilize one or more axially extending columns of tangs having tangs spaced at various distances from the head portion to provide locking of the nail when utilized with various thicknesses of insulation material and/or roof decks and the like. Examples of the prior art devices may be seen by reference to U.S. Pat. Nos. 2,740,505; 2,567,935 and 2,596,940.
The sheet metal nails of the prior art have been less than totally satisfactory as the tang or tangs closest the leading edge of the nail tended to be weakened and/or destroyed when the nail was driven into certain media. This is a particularly troublesome problem in a single tang type of nail and in those nails wherein the tangs most distant the head portion are relied upon to provide a locking action.